From the Kaby Lake PRM Vol. 7 "Assigning Conditional Flags":
* Note that the [post condition signal] bits generated at
the output of a compute are before the .sat.
Paragraph about post_zero does not mention saturation, but
testing it on actual GPUs shows that conditional modifiers
are applied after saturation.
* post_zero bit: This bit reflects whether the final
result is zero after all the clamping, normalizing,
or format conversion logic.
For signed types we don't care about saturation: it won't
change the result of conditional modifier.
For floating and unsigned types there two special cases,
when we can remove inst even if scan_inst is saturated: G
and LE. Since conditional modifiers are just comparations
against zero, saturating positive values to the upper
limit never changes the result of comparation.
For negative values:
(sat(x) > 0) == (x > 0) --- false
(sat(x) <= 0) == (x <= 0) --- true
Closes: https://gitlab.freedesktop.org/mesa/mesa/issues/2610
Signed-off-by: Yevhenii Kolesnikov <yevhenii.kolesnikov@globallogic.com>
Reviewed-by: Matt Turner <mattst88@gmail.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/4167>
Knowing following:
- CMP writes to flag register the result of
applying cmod to the `src0 - src1`.
After that it stores the same value to dst.
Other instructions first store their result to
dst, and then store cmod(dst) to the flag
register.
- inst is either CMP or MOV
- inst->dst is null
- inst->src[0] overlaps with scan_inst->dst
- inst->src[1] is zero
- scan_inst wrote to a flag register
There can be three possible paths:
- scan_inst is CMP:
Considering that src0 is either 0x0 (false),
or 0xffffffff (true), and src1 is 0x0:
- If inst's cmod is NZ, we can always remove
scan_inst: NZ is invariant for false and true. This
holds even if src0 is NaN: .nz is the only cmod,
that returns true for NaN.
- .g is invariant if src0 has a UD type
- .l is invariant if src0 has a D type
- scan_inst and inst have the same cmod:
If scan_inst is anything than CMP, it already
wrote the appropriate value to the flag register.
- else:
We can change cmod of scan_inst to that of inst,
and remove inst. It is valid as long as we make
sure that no instruction uses the flag register
between scan_inst and inst.
Nine new cmod_propagation unit tests:
- cmp_cmpnz
- cmp_cmpg
- plnnz_cmpnz
- plnnz_cmpz (*)
- plnnz_sel_cmpz
- cmp_cmpg_D
- cmp_cmpg_UD (*)
- cmp_cmpl_D (*)
- cmp_cmpl_UD
(*) this would fail without changes to brw_fs_cmod_propagation.
This fixes optimisation that used to be illegal (see issue #2154)
= Before =
0: linterp.z.f0.0(8) vgrf0:F, g2:F, attr0<0>:F
1: cmp.nz.f0.0(8) null:F, vgrf0:F, 0f
= After =
0: linterp.z.f0.0(8) vgrf0:F, g2:F, attr0<0>:F
Now it is optimised as such (note change of cmod in line 0):
= Before =
0: linterp.z.f0.0(8) vgrf0:F, g2:F, attr0<0>:F
1: cmp.nz.f0.0(8) null:F, vgrf0:F, 0f
= After =
0: linterp.nz.f0.0(8) vgrf0:F, g2:F, attr0<0>:F
No shaderdb changes
Closes: https://gitlab.freedesktop.org/mesa/mesa/issues/2154
Signed-off-by: Yevhenii Kolesnikov <yevhenii.kolesnikov@globallogic.com>
Reviewed-by: Matt Turner <mattst88@gmail.com>
Tested-by: Marge Bot <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/3348>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/3348>
It's not used by anything anymore now that so much lowering has been
moved into NIR. Sadly, we still need on in brw_compile_gs() for
geometry shaders on Sandy Bridge. Short of a lot of pointless work,
that one's probably not going away.
Reviewed-by: Kenneth Graunke <kenneth@whitecape.org>
There were two errors. First, the pass could propagate conditional
modifiers from an instruction that writes on flag register to an
instruction that writes a different flag register. For example,
cmp.nz.f0.0(16) null:F, vgrf6:F, vgrf5:F
cmp.nz.f0.1(16) null:F, vgrf6:F, vgrf5:F
could be come
cmp.nz.f0.0(16) null:F, vgrf6:F, vgrf5:F
Second, if an instruction writes f0.1 has it's condition propagated, the
modified instruction will incorrectly write flag f0.0. For example,
linterp(16) vgrf6:F, g2:F, attr0:F
cmp.z.f0.1(16) null:F, vgrf6:F, vgrf5:F
(-f0.1) discard_jump(16) (null):UD
could become
linterp.z.f0.0(16) vgrf6:F, g2:F, attr0:F
(-f0.1) discard_jump(16) (null):UD
None of these cases will occur currently. The only time we use f0.1 is
for generating discard intrinsics. In all those cases, we generate a
squence like:
cmp.nz.f0.0(16) vgrf7:F, vgrf6:F, vgrf5:F
(+f0.1) cmp.z(16) null:D, vgrf7:D, 0d
(-f0.1) discard_jump(16) (null):UD
Due to the mixed types and incompatible conditions, this sequence would
never see any cmod propagation. The next patch will change this.
No shader-db changes on any Intel platform.
v2: Fix typo in comment in test case subtract_delete_compare_other_flag.
Noticed by Caio.
Reviewed-by: Caio Marcelo de Oliveira Filho <caio.oliveira@intel.com>
Reviewed-by: Matt Turner <mattst88@gmail.com>
Tests like this should have been added in 4467040cb6 ("i965/fs:
Propagate conditional modifiers from not instructions").
Reviewed-by: Caio Marcelo de Oliveira Filho <caio.oliveira@intel.com>
Reviewed-by: Matt Turner <mattst88@gmail.com>
v2 (idr): Move adding the test to after adding the fix. Reordering the
two commits prevents possible headaches for git-bisect with scripts that
always do 'ninja check'.
Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=109404
Reviewed-by: Ian Romanick <ian.d.romanick@intel.com>
We emit an FBL instruction which only exists since Gen7. This prevents
the test from segfaulting when run with TEST_DEBUG=1.
Reviewed-by: Ian Romanick <ian.d.romanick@intel.com>
Mostly a dummy git mv with a couple of noticable parts:
- With the earlier header cleanups, nothing in src/intel depends
files from src/mesa/drivers/dri/i965/
- Both Autoconf and Android builds are addressed. Thanks to Mauro and
Tapani for the fixups in the latter
- brw_util.[ch] is not really compiler specific, so it's moved to i965.
v2:
- move brw_eu_defines.h instead of brw_defines.h
- remove no-longer applicable includes
- add missing vulkan/ prefix in the Android build (thanks Tapani)
v3:
- don't list brw_defines.h in src/intel/Makefile.sources (Jason)
- rebase on top of the oa patches
[Emil Velikov: commit message, various small fixes througout]
Signed-off-by: Emil Velikov <emil.velikov@collabora.com>
Reviewed-by: Jason Ekstrand <jason@jlekstrand.net>
2017-03-13 11:16:34 +00:00
Renamed from src/mesa/drivers/dri/i965/test_fs_cmod_propagation.cpp (Browse further)
